This invention relates to a novel lens in a vehicular lamp, a method of shaping the lens and an apparatus for shaping the lens. More particularly, the invention relates to technology for simplifying a mold structure for shaping a lens in a vehicular lamp.
It is known by for example Japanese Patent Unexamined Publication No. Hei. 7-186186 to form a lens for use in a vehicular lamp that is shaped from resin in at least two colors so that it has at least two integral portions of different colors. See FIGS. 12 and 13 in which a lens is indicated by a. The lens a usually has seal legs k that project generally to the back from the peripheral edges to form joints to the lamp body (not shown). If the lens has a curved section c, the seal leg b in that section includes two portions, a first portion d1 that corresponds to a lens surface a1 of on color, and a second portion d2 that corresponds to a lens surface a2 of another color. The first portion d1 is shaped from a resin of the first color whereas the second portion d2 is shaped from a resin of the second color.
The seal leg b in the curved section c has a portion that forms an undercut in the direction in which the shaped lens is to be removed from a shaping mold. To shape this portion of the seal leg, a sliding mold e must be used. If the seal leg portions d1 and d2 in the curved portion are shaped from resins of the same colors as the corresponding lens surfaces a1 and a2 the sliding mold for shaping the undercut has to be used each time a resin of a particular color is injected. In addition, a partition f must be used to ensure that a resin being shaped in one color will not enter the space for shaping a resin of another color. This increases the complexity of the mold structure and the efficiency and frequency of the mold maintenance operation is lowered accordingly.
An object, therefore, of the invention is to simplify the structure of a mold for shaping a lens in a vehicular lamp.
In accordance with a first aspect, the invention provides a lens for use in a vehicular lamp, in which a curved section is shaped from resin in at least two colors and the seal legs which at least form an undercut in the curved section are shaped from a resin having only one of said at least two colors.
Conventionally, the seal legs in the curved section of a multi-colored lens for use in a vehicular lamp are shaped using as many sliding molds as the number of colors from which it is formed. In contrast, the seal legs in the curved section of the multi-colored lens of the present invention are shaped from a resin of only one color and, hence, only one sliding mold need be used with the resulting advantage of helping to simplify the lens shaping mold.
According to a second aspect, the invention provides a method of shaping a lens for use in a vehicular lamp which comprises the steps of injecting a resin of a first color into a mold cavity to shape a part of the lens surface in the curved section and all seal legs which at least form an undercut in the curved section and injecting a resin of a second color into the mold cavity to shape an overlying portion that covers at least a portion of the front surface of the seal legs in the curved section that have been shaped by injection of the resin of the first color.
In one embodiment of the method according to the present invention, a resin of the first color shapes a part of the lens surface in the curved section and all seal legs which at least form an undercut in the curved section. Therefore, a sliding mold need be used only when injecting the resin of the first color and multi-color shaping can be accomplished without using a sliding mold when injecting resins of the second and any subsequent colors. In addition, no partition need be provided. As a result, the lens shaping mold and, hence, the overall shaping process is simplified.
According to a third aspect, the present invention provides an apparatus for shaping a lens for use in a vehicular lamp which comprises a first mold for shaping a resin of a first color and a second mold for shaping a resin of a second color, said first mold having a cavity for shaping a part of the lens surface in the curved section and a cavity for shaping all seal legs which at least form an undercut in the curved section, and said second mold having a cavity for shaping the other parts of the curved section and a cavity for shaping an overlying portion that covers at least a portion of the front surface of the seal legs in the curved section.
Thus, the inventive apparatus shapes all undercuts in a mold for shaping a resin of the first color and, therefore, a sliding mold need be provided in only this mold for shaping a resin of the first color. In addition, no partition need be provided. As a result, the shaping mold is simplified.